Hydraulic motor system

Abstract

A hydraulic motor includes a motor mechanism that rotates by hydraulic liquid that is supplied/discharged from a hydraulic liquid pressure source through one of a first motor passage and a second motor passage. The hydraulic motor comprises a casing that defines a casing chamber which accommodates the motor mechanism, and a flushing passage that is in communication with the casing chamber and extracts a portion of the hydraulic liquid from a low pressure side among the first motor passage and the second motor passage and leads it to the casing chamber.

The invention claimed is: 
     
       1. A hydraulic motor system equipped with a hydraulic motor that is configured to rotate by hydraulic liquid that is supplied/discharged from a hydraulic liquid pressure source through one of a first motor passage and a second motor passage, comprising:
 a casing that defines a casing chamber which accommodates the hydraulic motor; and 
 a flushing passage that is in communication with the casing chamber, is connected between the casing chamber and the first motor passage and between the casing chamber and the second motor passage, and is configured to extract a portion of the hydraulic liquid from a low pressure side among the first motor passage and the second motor passage and to provide the portion of the hydraulic liquid to the casing chamber, such that when a pressure in the first motor passage is lower than a pressure in the second motor passage, the flushing passage extracts the portion of the hydraulic liquid from the first motor passage, and when the pressure in the second motor passage is lower than the pressure in the first motor passage, the flushing passage extracts the portion of the hydraulic liquid from the second motor passage, 
 wherein the hydraulic motor includes:
 a swash plate provided in the casing chamber; 
 a plurality of pistons that are configured to move back and forth following the swash plate by hydraulic liquid pressure; 
 a cylinder block that is configured to rotate relative to the swash plate by the back-and-forth motion of the pistons; and 
 an output shaft that is configured to output the rotation of the cylinder block, 
 
 wherein the casing includes:
 a base plate in which the first motor passage and the second motor passage are provided; and 
 a case that supports the output shaft and defines the casing chamber together with the base plate, 
 
 wherein the flushing passage is defined by:
 a base-side flushing through hole that is formed in the base plate; and 
 a case-side flushing through hole that is formed in the case, a one end of the case-side flushing through hole being in communication with the base-side flushing through hole, and another end of the case-side flushing through hole being in communication with the casing chamber, 
 
 wherein the hydraulic liquid extracted from the flushing passage and guided to the casing chamber is discharged through a drain passage, and 
 wherein the drain passage includes a drain through hole that is formed in the case, a one end of the drain through hole being in communication with the casing chamber so as to oppose the another end of the case-side flushing through hole. 
 
     
     
       2. The hydraulic motor system according to  claim 1 , wherein the base-side flushing through hole is formed to pass through the base plate in axial direction. 
     
     
       3. A hydraulic motor system equipped with a hydraulic motor that is configured to rotate by hydraulic liquid that is supplied/discharged from a hydraulic liquid pressure source through one of a first motor passage and a second motor passage, comprising:
 a casing that defines a casing chamber which accommodates the hydraulic motor; 
 a flushing passage that is in communication with the casing chamber, is connected between the casing chamber and the first motor passage and between the casing chamber and the second motor passage, and is configured to extract a portion of the hydraulic liquid from a low pressure side among the first motor passage and the second motor passage and to provide the portion of the hydraulic liquid to the casing chamber, such that when a pressure in the first motor passage is lower than a pressure in the second motor passage, the flushing passage extracts the portion of the hydraulic liquid from the first motor passage and when the pressure in the second motor passage is lower than the pressure in the first motor passage, the flushing passage extracts the portion of the hydraulic liquid from the second motor passage; 
 a brake disc; and 
 a drain passage that is configured to discharge hydraulic liquid of the casing chamber, 
 wherein the hydraulic motor includes:
 a swash plate provided in the casing chamber; 
 a plurality of pistons that are configured to move back and forth following the swash plate by hydraulic liquid pressure; 
 a cylinder block that is configured to rotate relative to the swash plate by the back-and-forth motion of the pistons, the cylinder block being configured to rotate together with the brake disc; and 
 an output shaft that is configured to output the rotation of the cylinder block, 
 
 wherein the casing includes:
 a base plate in which the first motor passage and the second motor passage are provided; and 
 a case that supports the output shaft and defines the casing chamber together with the base plate, 
 
 wherein the flushing passage is defined by:
 a base-side flushing through hole that is formed in the base plate; and 
 a case-side flushing through hole that is formed in the case and is in communication with the base-side flushing through hole, 
 
 wherein a swash plate housing chamber that houses the swash plate and a brake front chamber that is partitioned from the swash plate housing chamber by the brake disc are defined in the casing chamber, and 
 wherein an outlet of the flushing passage and an inlet of the drain passage each open into the swash plate housing chamber. 
 
     
     
       4. The hydraulic motor system according to  claim 3 , wherein the drain passage is defined by a plurality of drain through holes that open into the casing chamber. 
     
     
       5. A hydraulic motor system equipped with a hydraulic motor that is configured to rotate by hydraulic liquid that is supplied/discharged from a hydraulic liquid pressure source through one of a first motor passage and a second motor passage, comprising:
 a casing that defines a casing chamber which accommodates the hydraulic motor; 
 a low pressure selective valve connected to an end of the first motor passage and an end of the second motor passage, the low pressure selective valve comprising a spool movable linearly within a space in the casing, the spool including a groove; and 
 a flushing passage connected between the low pressure selective valve and the casing chamber and in fluid communication with a portion of the space in the casing in which the groove is located, 
 wherein the first motor passage and the second motor passage are in fluid communication with the space in the casing, 
 wherein the first motor passage is in fluid communication with a first chamber at a first end of the spool and exerts pressure against the first end of the spool, and the second motor passage is in fluid communication with a second chamber at a second end of the spool opposite the first end and exerts pressure against the second end of the spool, 
 wherein the low pressure selective valve is configured to switch according to a pressure in the first motor passage and the second motor passage, such that one of the first motor passage and the second motor passage having a lower pressure is connected to the flushing passage via the groove in the spool to provide hydraulic liquid from the hydraulic liquid pressure source to the casing chamber, 
 wherein the hydraulic motor includes:
 a swash plate provided in the casing chamber; 
 a plurality of pistons that are configured to move back and forth following the swash plate by hydraulic liquid pressure; 
 a cylinder block that is configured to rotate relative to the swash plate by the back-and-forth motion of the pistons; and 
 an output shaft that is configured to output the rotation of the cylinder block, 
 
 wherein the casing includes:
 a base plate in which the first motor passage and the second motor passage are provided; and 
 a case that supports the output shaft and defines the casing chamber together with the base plate, 
 
 wherein the flushing passage is defined by
 a base-side flushing through hole that is formed in the base plate; and 
 a case-side flushing through hole that is formed in the case, a one end of the case-side flushing through hole being in communication with the base-side flushing through hole, and another end of the case-side flushing through hole being in communication with the casing chamber, 
 
 wherein the hydraulic liquid extracted from the flushing passage and guided to the casing chamber is discharged through a drain passage, and 
 wherein the drain passage includes a drain through hole that is formed in the case, a one end of the drain through hole being in communication with the casing chamber so as to oppose to the another end of the case-side flushing through hole. 
 
     
     
       6. The hydraulic motor system according to  claim 5 , wherein the first motor passage is in fluid communication with the space in the casing via a first opening and the second motor passage is in fluid communication with the space in the casing via a second opening, and
 a length of the groove in the spool is less than a distance between the first opening and the second opening.